I have a stand-alone installation of VMWare vSphere Essentials, with a vCenter Server and 3 ESXi 4.0 host servers. The environment is intended to remain as a stand-alone network, with the exception that I can "float" a workstation or server between the 'Net and the VMWare network for patches and maintenance.

With other installations, where the Internet is available, I've used the vSphere Host Update utility to connect to VMWare and then apply the patches to the ESXi hosts.

My problem is that this utility does not seem to function if it cannot connect to both VMWare and the ESXi host at the same time, as the scan for patches function will not scan the server without connecting to VMWare's site to sync its repository first. Even if I sync it, disconnect from the 'Net and connect to the VMWare network, it still won't scan hosts for required patches -- it will prompt for syncing with VMWare and if you click No to syncing, the scan does not occur.

Does anyone know of other options for updating the ESXi hosts in some automated fashion?
I believe I can manually pull down required patches and apply them, but this will not scale well, and in the future I'm sure I'll want something a bit more scalable.

If you install VCUM onto the VC box it creates an update respository postbox directory, you can manually copy updates/patched etc. into that, not sure if you need to restart VCUM for it to recognise the new files but either way it will add them to the catalogue for you to add to a baseline and remediate to your heart's content.

This is not ideal, but it works best for the ESX environment I maintain. We have some hosts with RAID controllers and NICs that aren't on the HCL so updates will generally fail on those and require manual intervention anyway.

Get the full install ISO for the version you want.

Put the host to upgrade into maintenance mode via vSphere or VirtualCenter. All the guests will be migrated to other hosts at this point.

Shutdown the host once all migrations are done.

Clean install ESX/ESXi and configure it for the network with the same hostname and ip address.

Connect it back into vSphere or VirtualCenter and finish configuration so it matches the rest of the hosts in the cluster.

Migrate some machines back to it and repeat as necessary.

If your upgrade process requires a vSphere or VirtualCenter upgrade do that first. There are some tradeoffs by doing it this way, but for our purposes and in our current environment it is the most reliable and fastest way to get the upgrades done. If the auto-upgrade doesn't workout for some reason you have something like the above to fall back to.